Here's a 2nd link indicating you may be able to buy with:
A 3.5% down payment if you have a min credit score of 580+.
A 10% down payment if you have a min credit score of 500-579.
Since your goal is to own the home you should simply purchase the home yourself. I assume your Aunt is moving in with her daughter to either reduce costs, be cared for or a combination of the two. If you buy the home outright you avoid any legal issues down the road and I'm sure your Aunt will feel more secure knowing she has reserve funds for her care and no more property related payments. Plus, as Sally/Neil comment, most mortgages are not assumable and legal issues can arise by just taking over payments.
The best way to proceed if you are interested in purchasing the property is to obtain a true Pre-Approval: http://www.Steven-Anthony.com/GettingStarted
Of course, "bad credit" is a factor; however, there are different levels of â€œbad creditâ€. For example, FHA financing only requires a 580 credit score to qualify (and can be lower if you are putting down 10%), and you indicate you make a good salary! From http://portal.hud.gov/hudportal/HUD?src=/press/press_release
"New borrowers will now be required to have a minimum FICO score of 580 to qualify for FHA's 3.5% down payment program. New borrowers with less than a 580 FICO score will be required to put down at least 10%."
[Confirm this information with a FHA Loan Broker/Banker]
Regarding Credit Scores:
Not sure you should move forward because of your current FICO credit score range?
See the "FICOÂ® Score Estimator" at http://www.myfico.com/FICOCreditScoreEstimator/Estimator.aspx
Back when I was mortgage brokering/banking I found this to be about 85% accurate! Of course, if you move forward with a true Pre-Approval you will know your actual FICO mid-score to used (there are three scores, lenders use the â€œmiddle scoreâ€ for qualification purposes), but this might be a good place to start!
Best of luck!
If what you want is to continue paying the mortgage that is in someone elses name you can do that. Once that mortgage is paid in full it's gone. Getting the house into your name involves having the person who's name it is in now to "sign it over" to you. What you have to worry about is if that person should pass while you are paying it off. That person could sign it over to you now but chances are that would trigger a clause by the bank to make the entire loan payable instantly. I would suggest you consult an attorney NOW and have him/her create an agreement between you and the person who holds title.
The other option is to simply "buy" the house from the current owner. That involves you qualifying for a new loan. If there is substantial equity in the property and you have a good income you might still qualify even if you have poor credit. You wont know until you try and it costs nothing to try.